1. Field of the Invention
This invention relates to an aromatic polysulfone resin composition which is improved in the dispersibility of fluorocarbon polymer in the aromatic polysulfone matrix comprising a specified fluorocarbon polymer and an aromatic polysulfone resin. More particularly, this invention relates to an aromatic polysulfone resin composition improved in appearance, mechanical strength, sliding characteristics, moldability, etc. of molded product.
2. Description of the Prior Art
Since aromatic polysulfone resin is amorphous, it has isotropy and is small in mold shrinkage. Further, since it is higher in glass transition point than high heat resistance resins such as polyphenylene sulfide and polyether-ketone, it retains smaller extents of deterioration in strength, modulus of elasticity, creep resistance, etc. up to a higher temperature as compared with these resins. Thus, aromatic polysulfone resin is successfully usable as a material of electronic parts and parts of OA, AV instruments which must have a high dimensional accuracy and a high heat resistance.
A composition prepared by adding a fluorocarbon polymer, preferably polytetrafluorethylene, to an aromatic polysulfone resin has a self-lubricating property in addition to the above-mentioned properties, and therefore it is improved in mold release characteristics from mold and sliding characteristics, as is well known.
Further, it is mentioned in Japanese Patent Application Kokai (Laid-Open) No. 60-23448 that, in case of aromatic polysulfone resin compositions containing a fibrous reinforcing material such as glass fiber, potassium titanate fiber, wollastonite and the like or containing an inorganic filler such as talc, calcium carbonate, glass beads and the like, mold shrinkage of the composition is reduced and therefore mold release characteristics of such compositions from mold can be remarkably improved by adding a fluorocarbon polymer to them. Further, regarding sliding characteristics, it is mentioned in Japanese Patent Kokai (Laid-Open) No. 60-38465 that a composition comprising an aromatic polysulfone, a fluorocarbon polymer and carbon fiber is excellent in wear characteristics and brings about an improvement in bearing life when used as an oilless bearing. Further, it is mentioned in Japanese Patent Kokai (Laid-Open) No. 58-160353 that, when a composition comprising an aromatic polysulfone, a fluorocarbon polymer and oxybenzoyl polyester is used as an oilless bearing, the bearing has excellent wear characteristics and an improved bearing life and, in addition, it does not injure the opposite material even if the latter is made of a soft metal such as aluminum, SUS and the like.
Although the fluorocarbon polymer used in the above-mentioned compositions, particularly polytetrafluorethylenes represented by Fluon.RTM. L169J and L170J manufactured by Asahi Glass Fiber Co. or Lublon.RTM. L-2 and L-5 manufactured by Daikin Industries, Ltd. have a melting point ranging from 325.degree. C. to 330.degree. C., their molten products have a very high melt viscosity or are hardly flowable at the molding temperature of aromatic polysulfone resin (350.degree. C. or above). Accordingly, if an aromatic polysulfone resin is mixed with such a fluorocarbon polymer and molded by extrusion or injection, the fluorocarbon polymer is aggregated by the shearing action and its dispersibility in the aromatic polysulfone matrix is much deteriorated. Thus, the molded product is inferior in appearance and low in mechanical strength. Further, this type of compositions are waiting for an additional improvement in sliding characteristics.